The invention relates to an apparatus for vibration isolation attachment of a subframe or aggregate holder at a support member of a main frame structure of a motor vehicle under the disposition of an elastic bearing with a metal bearing core and with a sheet metal cover connected by vulcanizing thereto, whereby the bearing core is connected at its front side with the support member of the main frame structure.
DE-OS (German unexamined published application) No. 29 30 695 makes known an elastic bearing for the attachment of a subframe at a support member of a frame of a motor vehicle. The subframe is connected to the bearing with an elastic bushing whereby the bearing core or shaft is held at the frame support member by means of an interposed pot-shaped bracket. The frame support member is formed with a cross section having a U-shaped profile and is closed or covered by means of a bottom or floor plate. This arrangement exhibits the disadvantage that vibrations caused by uneven road surfaces or other special influences are transmitted through the bearing to the frame support members of the frame structure and cause disturbing noises.
The invention is concerned with the problem of creating an apparatus of the above-mentioned type, wherein the transmission of vibrations to the basic frame structure of the motor vehicle caused by the dynamics of vehicle driving are substantially avoided.
This problem is inventably solved by providing that the subframe is supported at the mainframe support member by way of a bearing with an elastic bushing having a large support area base at the bearing core and by providing impedance increasing elements in the region of the bearing support, which elements form a vibration obstructing or deflecting plane between the elastic bearing and the main frame support member.
A principal advantage obtained with the invention is that the vibrations from the vehicle wheels of different orders of magnitude that are transmitted to the subframe are further transferred to the support member of the main frame only after they have been strongly damped, since a separating plane is created at the separating point of the support member and the support surface of the bearing core or shaft. This advantage is obtained by means of point support reinforcement of the support member in the anchoring region of the bearing as well as by means of vibration resistant point masses acting against the vibrations. The increased impedance of the stiffening, or reinforcement as well as the mass accummulation in the region of the bearing results in an insensitivity with respect to the transmitted vibrations from the subframe via the elastic bearing. The support of the bearing core at the frame support member is provided with a large input impedance loaded support area, thereby resulting in a high vibration damping with respect to the vehicle body.
The elastic bearing is so constructed that the subframe can be assembled with the bearing in a simple manner. The elastic bearing is pressed into a corresponding opening of the subframe beam or girder and is further connected together with the frame support member bearer or beam. At the circumference of the elastic part of the bearing, a clamping seat is provided with a fixed or rigid abutment for yieldingly supporting the subframe support member in its verticle primary loading direction. Opposite this abutment an annular ring is provided on the elastic part for clamping and griping the subframe support member at its underside. Simultaneously this annular ring serves as an elastic abutment part during tension loading of the subframe. To balance undesirable tolerance conditions as well as to provide initial damping for vibrations, an elastic layer is provided between the subframe and a sheet metal cover of the elastic bearing. This elastic layer exhibits a thickness and profile shape (ribs and the like) corresponding to the tolerances and required characteristics.
An exemplary embodiment of the invention is shown in the drawings and described in more detail in the following description.
These and further objects, features and advantages of the present invention will become more obvious from the following description when taken in connection with the accompanying drawings which shows, for purposes of illustration only, several embodiments in accordance with the present invention.